The need for round-the-clock military operations has resulted in the use of night-vision goggles (NVG). These goggles amplify the lighting in the red and infrared regions of the electromagnetic system. Lighting in the crew station or cockpit of an aircraft should be filtered so that it will not impair the operation of these goggles and be visible to the unaided eye.
In the cockpit is an annunciator panel (caution and advisory panel) mounted on the instrument panel which consists of a number of lighted cartridges, generally amber in color which extend from the base of the cockpit front panel. Adaptation of the panel for NVG can be accomplished by several methods. The first is by opening the individual cartridges and replacing the amber colored filters with blue-green filters. The problem with this is that it is suspected that the messages can be lighted to a sufficient intensity to be visible in high ambient light conditions such as sunlight. In this case, it would result in a dedicated panel or reworking the panel constantly as the mission changes from night to day or interchanging the entire annunciator panel with a daylight panel. Another solution would be to cover the entire annunciator panel with a large blue-green filter. The problem with this is stowage when it is not needed and having it readily available for use. Hinging a panel of this size, approximately 5".times.5.2" about a vertical or horizontal axis would present a visual obstruction or interfere with axis to switches on the instrument panel.
Preferably, therefore, a filter is needed which can be removed to provide sunlight readability. It must also be retained as part of the instrument panel.